This chapter is from the book
This chapter is from the book
This chapter is from the book
Enter WPF
Microsoft recognized that something brand new was needed that escaped the limitations of GDI+ and USER yet provided the kind of productivity that people enjoy with frameworks like Windows Forms. And with the continual rise of cross-platform applications based on HTML and JavaScript, Windows desperately needed a technology that’s as fun and easy to use as these, yet with the power to exploit the capabilities of the local computer. Windows Presentation Foundation (WPF) is the answer for software developers and graphic designers who want to create modern user experiences without having to master several difficult technologies. Although “Presentation” sounds like a lofty term for what I would simply call a user interface, it’s probably more appropriate for describing the higher level of visual polish that’s expected of today’s applications and the wide range of functionality included in WPF!
The highlights of WPF include the following:
-
Broad integration—Prior to WPF, a Windows developer who wanted to use 3D, video, speech, and rich document viewing in addition to normal 2D graphics and controls would have to learn several independent technologies with a number of inconsistencies and attempt to blend them together without much built-in support. But WPF covers all these areas with a consistent programming model as well as tight integration when each type of media gets composited and rendered. You can apply the same kind of effects consistently across different media types, and many of the techniques you learn in one area apply to all the other areas.
-
Resolution independence—Imagine a world in which moving to a higher resolution or DPI setting doesn’t mean that everything gets smaller; instead, graphics and text simply get crisper! Envision user interfaces that look reasonable on a small netbook as well as on a 60-inch TV! WPF makes this easy and gives you the power to shrink or enlarge elements on the screen independently from the screen’s resolution. A lot of this is possible because of WPF’s emphasis on vector graphics.
-
Hardware acceleration—WPF is built on Direct3D, so content in a WPF application—whether 2D or 3D, graphics, or text—is converted to 3D triangles, textures, and other Direct3D objects and then rendered by hardware. This means that WPF applications get the benefits of hardware acceleration for smoother graphics and all-around better performance (due to work being offloaded to graphics processing units [GPUs] instead of central processor units [CPUs]). It also ensures that all WPF applications (not just high-end games) receive benefits from new hardware and drivers, whose advances typically focus on 3D capabilities. But WPF doesn’t require high-end graphics hardware; it has a software rendering pipeline as well. This enables features not yet supported by hardware, enables high-fidelity printing of any content on the screen, and is used as a fallback mechanism when encountering inadequate hardware resources (such as an outdated graphics card or even a high-end one that has simply run out of GPU resources such as video memory).
-
Declarative programming—Declarative programming is not unique to WPF, as Win16/Win32 programs have used declarative resource scripts to define the layout of dialog boxes and menus for over 25 years. And .NET programs of all types often leverage declarative custom attributes plus configuration and resource files based on Extensible Markup Language (XML). But WPF takes declarative programming to the next level with Extensible Application Markup Language (XAML; pronounced “Zammel”). The combination of WPF and XAML is similar to using HTML to define a user interface—but with an incredible range of expressiveness. This expressiveness even extends beyond the bounds of user interfaces; WPF uses XAML as a document format, a representation of 3D models, and more. The result is that graphic designers are empowered to contribute directly to the look and feel of applications, as well as some behavior for which you’d typically expect to have to write code. The next chapter examines XAML in depth.
-
Rich composition and customization—WPF controls can be composed in ways never before seen. You can create a ComboBox filled with animated Buttons or a Menu filled with live video clips! Although these particular customizations might sound horrible, it’s important that you don’t have to write a bunch of code (or any code!) to customize controls in ways that the control authors never imagined (unlike owner-draw in prior technologies). Along the same lines, WPF makes it quite easy to “skin” applications with radically different looks (covered in Chapter 14, “Styles, Templates, Skins, and Themes”).
In short, WPF aims to combine the best attributes of systems such as DirectX (3D and hardware acceleration), Windows Forms (developer productivity), Adobe Flash (powerful animation support), and HTML (declarative markup). With the help of this book, I think you’ll find that WPF gives you more productivity, power, and fun than any other technology you’ve worked with in the past!
Faq: Does WPF enable me to do something that I couldn’t have previously done?
Technically, the answer is “No,” just like C# and the .NET Framework don’t enable you to do something that you couldn’t do in assembly code. It’s just a question of how much work you want to do to get the desired results!
If you were to attempt to build a WPF-equivalent application from scratch without WPF, you’d not only have to worry about the drawing of pixels on the screen and interaction with input devices, you’d also need to do a ton of additional work to get the accessibility and localization support that’s built in to WPF, and so on. WPF also provides the easiest way to take advantage of Windows 7 features, such as defining Jump List items with a small chunk of XAML (see Chapter 8, “Exploiting Windows 7”).
So I think most people would agree that the answer is “Yes” when you factor time and money into the equation!
Faq: When should I use DirectX instead of WPF?
DirectX is more appropriate than WPF for advanced developers writing hard-core “twitch games” or applications with complex 3D models where you need maximum performance. That said, it’s easy to write a naive DirectX application that performs far worse than a similar WPF application.
DirectX is a low-level interface to the graphics hardware that exposes all the quirks of whatever GPU a particular computer has. DirectX can be thought of as assembly language in the world of graphics: You can do anything the GPU supports, but it’s up to you (the application author) to support all the hardware variations. This is onerous, but such low-level hardware access enables skilled developers to make their own tradeoffs between fine-grained quality and speed. In addition, DirectX exposes cutting-edge features of GPUs as they emerge more quickly than they appear in WPF.
In contrast, WPF provides a high-level abstraction that takes a description of a scene and figures out the best way to render it, given the hardware resources available. (It’s a retained mode system rather than an immediate mode system.) 2D is the primary focus of WPF; its 3D support is focused on data visualization scenarios and integration with 2D rather than supporting the full power of DirectX.
The downside of choosing DirectX over WPF is a potentially astronomical increase in development cost. A large part of this cost is the requirement to test an application on each driver/GPU combination you intend to support. One of the major benefits of building on top of the WPF is that Microsoft has already done this testing for you! You can instead focus your testing on low-end hardware for measuring performance. The fact that WPF applications can even leverage the client GPU in a partial-trust environment is also a compelling differentiator.
Note that you are able to use both DirectX and WPF in the same application. Chapter 19, “Interoperability with Non-WPF Technologies,” shows how this can be done.